scholarly journals Mechanical Characterisation and Shrinkage of Thermoactivated Recycled Cement Concrete

2021 ◽  
Vol 11 (6) ◽  
pp. 2454
Author(s):  
Sofia Real ◽  
José Alexandre Bogas ◽  
Ana Carriço ◽  
Susana Hu
Keyword(s):  
Mechanical Strength ◽  
Elasticity Modulus ◽  
Ultrasonic Pulse Velocity ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
Cement Concrete ◽  
Supplementary Cementitious Material ◽  
Mechanical Characterisation ◽  
Shrinkage Behaviour ◽  
Binder Ratio

This paper investigates the mechanical and shrinkage behaviour of concrete with recycled cement (RC) thermoactivated from waste cement paste and waste concrete. Overall, compared to ordinary Portland cement (OPC), for the same water/binder ratio, the mechanical strength and ultrasonic pulse velocity were not significantly influenced by the incorporation of RC. The elasticity modulus decreased with the addition of RC and the shrinkage tended to increase at high RC content. The incorporation of up to 15% RC allowed the production of workable concrete with identical shrinkage and similar to higher mechanical strength than concrete with only OPC. RC proved to be a very promising more eco-efficient supplementary cementitious material.

scholarly journals The Hydration, Mechanical, Autogenous Shrinkage, Durability, and Sustainability Properties of Cement–Limestone–Slag Ternary Composites

2021 ◽  
Vol 13 (4) ◽  
pp. 1881
Author(s):  
Mei-Yu Xuan ◽  
Yi Han ◽  
Xiao-Yong Wang
Keyword(s):  
Compressive Strength ◽  
Electrical Resistivity ◽  
Experimental Studies ◽  
Autogenous Shrinkage ◽  
Ultrasonic Pulse Velocity ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
Hydration Heat ◽  
Granulated Blast Furnace Slag ◽  
Binder Ratio

This study examines the hydration–mechanical–autogenous shrinkage–durability–sustainability properties of ternary composites with limestone filler (LF) and ground-granulated blast furnace slag (BFS). Four mixtures were prepared with a water/binder ratio of 0.3 and different replacement ratios varying from 0 to 45%. Multiple experimental studies were performed at various ages. The experimental results are summarized as follows: (1) As the replacement levels increased, compressive strength and autogenous shrinkage (AS) decreased, and this relationship was linear. (2) As the replacement levels increased, cumulative hydration heat decreased. At the age of 3 and 7 days, there was a linear relationship between compressive strength and cumulative hydration heat. (3) Out of all mixtures, the ultrasonic pulse velocity (UPV) and electrical resistivity exhibited a rapid increase in the early stages and tended to slow down in the latter stages. There was a crossover of UPV among various specimens. In the later stages, the electrical resistivity of ternary composite specimens was higher than plain specimens. (4) X-ray diffraction (XRD) results showed that LF and BFS have a synergistic effect. (5) With increasing replacement ratios, the CO2 emissions per unit strength reduced, indicating the sustainability of ternary composites.

scholarly journals Utilization of Metakaolin and Calcite: Working Reversely in Workability Aspect—As Mineral Admixture in Self-Compacting Concrete

2018 ◽  
Vol 2018 ◽  
pp. 1-12
Author(s):  
Fatih Özcan ◽  
Halil Kaymak
Keyword(s):  
Compressive Strength ◽  
High Strength ◽  
High Volume ◽  
Ultrasonic Pulse Velocity ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
Mineral Admixture ◽  
Self Compacting Concrete ◽  
Binder Ratio

In this work, utilization of metakaolin (MK) and calcite (C), working reversely in workability aspect, as mineral admixture in self-compacting concrete (SCC), was investigated. MK and C replaced cement in mass basis at various replacement ratios, separately and together. In total, 19 different SCCs were produced. Binder content and water to binder ratio were selected as 500 kg/m3 and 0.4, respectively. Workability tests including slump flow, T50, L-box, and V-funnel tests were performed. Consistency and setting times of binder paste were measured. While replacement of MK with cement increased the amount of plasticiser requirement, calcite worked reversely and decreased it. Reverse influence of MK and C on plasticiser requirement of SCC made possible to produce SCC at total 45% replacement ratio of MK and C together. Samples of SCC were cured in water at 20°C temperature. Compressive strengths of SCC samples were measured up to six months to evaluate the influence of MK and C, separately and together. Ultrasonic pulse velocity, abrasion, and capillary water absorption values of samples were determined at specified age. MK inclusion in concrete reduces workability, while C inclusion increases it. C and MK inclusion together remedied workability of concrete and enabled to produce SCC with high volume of admixtures. Furthermore, C incorporation increased one-day compressive strength, while MK incorporation reduced it in comparison with control concrete. In long term, C inclusion reduced compressive strength; however, MK inclusion increased it. C inclusion remedied one-day strength of concrete when it was used together with MK. MK inclusion remedied long-term compressive strength when it was used together with C and enabled to produce high-strength SCC with high volume of admixtures. SCC containing MK and C together showed better durability-related property.

scholarly journals Effect of Using Limestone Fines on the Chemical Shrinkage of Pastes and Mortars

2021 ◽  
Author(s):  
Jamal Khatib ◽  
Rawan Ramadan ◽  
Hassan Ghanem ◽  
Adel ElKordi
Keyword(s):  
Compressive Strength ◽  
Ultrasonic Pulse Velocity ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
Chemical Shrinkage ◽  
Total Period ◽  
Binder Ratio ◽  
Limestone Fines ◽  
Water To Binder Ratio

Abstract The main aim of this study is to examine the effect of incorporating limestone fines (LF) on chemical shrinkage of pastes and mortars. For this purpose, five paste and five mortar mixes were prepared with 0, 5, 10, 15 and 20% (by weight) LF as replacement of cement. The water to binder ratio (w/b) was 0.45 for all mixes. The sand to binder (s/b) ratio in the mortar mixes was 2. Testing included chemical shrinkage, compressive strength, density and ultrasonic-pulse velocity (UPV). Chemical shrinkage was tested each hour for the first 24 hrs, and thereafter each 2 days until a total period of 90 days. Furthermore, compressive strength and UPV tests were conducted at 1 day, 7, 28 and 90 days of curing. The results show that the long-term chemical shrinkage of pastes was found to increase with the increase in LF content up to 15%. Beyond this level of replacement, the chemical shrinkage started to decrease. However, the chemical shrinkage for mortars increased with the increase in LF content up to 10% LF and a decrease was observed beyond this level. It was also noticed that compressive strength for pastes and mortars attained the highest value for mixes containing 10 and 15% LF. The trend in the UPV results is somewhat similar to those of strength. Density for pastes and mortars increased up to 15% LF followed by a decrease at 20 % replacement level. Correlations between the various properties were conducted. It was found that an increase in chemical shrinkage led to an increase in compressive strength.

PENGKAJIAN KEKUATAN BETON STRUKTUR JEMBATAN PASCA KEBAKARAN

2013 ◽  
Vol 12 (3) ◽  
Author(s):  
Sudarmadi Sudarmadi
Keyword(s):  
Compressive Strength ◽  
Concrete Strength ◽  
Ultrasonic Pulse Velocity ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
Test Results ◽  
Concrete Compressive Strength ◽  
Strength Assessment ◽  
Concrete Testing

In this paper a case study about concrete strength assessment of bridge structure experiencing fire is discussed. Assessment methods include activities of visual inspection, concrete testing by Hammer Test, Ultrasonic Pulse Velocity Test, and Core Test. Then, test results are compared with the requirement of RSNI T-12-2004. Test results show that surface concrete at the location of fire deteriorates so that its quality is decreased into the category of Very Poor with ultrasonic pulse velocity ranges between 1,14 – 1,74 km/s. From test results also it can be known that concrete compressive strength of inner part of bridge pier ranges about 267 – 274 kg/cm2 and concrete compressive strength of beam and plate experiencing fire directly is about 173 kg/cm2 and 159 kg/cm2. It can be concluded that surface concrete strength at the location of fire does not meet the requirement of RSNI T-12-2004. So, repair on surface concrete of pier, beam, and plate at the location of fire is required.

scholarly journals Correlation between Uniaxial Compression Test and Ultrasonic Pulse Rate in Cement with Different Pozzolanic Additions

2021 ◽  
Vol 11 (9) ◽  
pp. 3747
Author(s):  
Leticia Presa ◽  
Jorge L. Costafreda ◽  
Domingo Alfonso Martín
Keyword(s):  
Compression Test ◽  
Ultrasonic Pulse Velocity ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
Uniaxial Compression Test ◽  
Unconfined Compression Test ◽  
Pozzolanic Cement ◽  
The Relationship ◽  
Compression Resistance

This work aims to study the relationship between the compression resistance and velocity from ultrasonic pulses in samples of mortars with 25% of pozzolanic content. Pozzolanic cement is a low-priced sustainable material that can reduce costs and CO2 emissions that are produced in the manufacturing of cement from the calcination of calcium carbonate. Using ultrasonic pulse velocity (UPV) to estimate the compressive resistance of mortars with pozzolanic content reduces costs when evaluating the quality of structures built with this material since it is not required to perform an unconfined compression test. The objective of this study is to establish a correlation in order to estimate the compression resistance of this material from its ultrasonic pulse velocity. For this purpose, we studied a total of 16 cement samples, including those with additions of pozzolanic content with different compositions and a sample without any additions. The results obtained show the mentioned correlation, which establishes a basis for research with a higher number of samples to ascertain if it holds true at greater curing ages.

scholarly journals Physicochemical, Mineralogical, and Mechanical Properties of Calcium Aluminate Cement Concrete Exposed to Elevated Temperatures

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3855
Author(s):  
Amirmohamad Abolhasani ◽  
Bijan Samali ◽  
Fatemeh Aslani
Keyword(s):  
Temperature Rise ◽  
Calcium Aluminate ◽  
Elevated Temperatures ◽  
Ultrasonic Pulse Velocity ◽  
Pulse Velocity ◽  
Calcium Aluminate Cement ◽  
Cement Concrete ◽  
Sem Images ◽  
Strength Deterioration ◽  
Aluminate Cement

One commonly used cement type for thermal applications is CAC containing 38–40% alumina, although the postheated behavior of this cement subjected to elevated temperature has not been studied yet. Here, through extensive experimentation, the postheated mineralogical and physicochemical features of calcium aluminate cement concrete (CACC) were examined via DTA/TGA, X-ray diffraction (XRD), and scanning electron microscopy (SEM) imaging and the variation in the concrete physical features and the compressive strength deterioration with temperature rise were examined through ultrasonic pulse velocity (UPV) values. In addition, other mechanical features that were addressed were the residual tensile strength and elastic modulus. According to the XRD test results, with the temperature rise, the dehydration of the C3AH6 structure occurred, which, in turn, led to the crystallization of the monocalcium dialuminate (CA2) and alumina (Al2O3) structures. The SEM images indicated specific variations in morphology that corresponded to concrete deterioration due to heat.

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